One well known technique for providing electric motor armature insulation is disclosed in the Perkins U.S. Pat. No. 2,831,991, Apr. 22, 1958, in which core end laminations of insulating material are fabricated separately and require individual handling during assembly of the motor armature. This construction is ill-suited to automated motor fabricating methods.
Studer the U.S. Pat. No. 2,232,812, Feb. 25, 1941, discloses an armature insulation arrangement in which layers of insulating material covering each end of the armature core laminations are formed integrally with core slot insulation. This insulation arrangement, whether molded separately and applied to the armature or molded directly onto the armature core laminations, requires complicated and expensive molds and seriously detracts from the cross sectional space available for wire coils in the core lamination slots.
Robinson et al The U.S. Pat. No. 3,917,967, Nov. 4, 1975, discloses a motor armature insulation arrangement in which molded insulating material is applied between the shaft and armature coil laminations and against the end laminations of the armature core but only to a diameter approximating the root diameter of the armature core slots. The annular recesses in the insulating material adjacent each armature coil end lamination, which are important in the Robinson et al teaching, would require complicated molds not conducive to cost effective production methods.